1. Field of the Invention
This invention relates to a lubricating composition, and, in particular, to manual transmission fluids.
2. Description of the Art Practices
Transmission fluids, particularly those for synchromesh manual transmissions, have typically been based upon fluids described for other purposes such as engine oils, differential oils and automatic transmission fluids. The lighter of these oils, e.g., automatic transmission fluid, thins out too much at the high temperatures reached during summertime driving resulting in objectional gear noise or hot rattle. While the heavier of these oils are acceptable under normal summertime driving conditions, difficulties are often encountered in cold weather conditions. The viscosity of the heavier mineral oils increases substantially in the winter due to low temperatures. The shifting characteristics for the manual transmission are then significantly hindered due to the thickened oil.
A second problem which faces a synchromesh transmission is that of double detent or double bump. This phenomena results when the static coefficient of friction is too high and the engaging sleeve chamfer cannot engage readily with the cone chamfer due to insufficient slippage to allow smooth engaging. A further problem arises if the dynamic coefficient of friction is too low as clashing is observed. The clashing arises because the relative velocity of the blocker ring and cone assembly does not go to zero as engagement proceeds.
Given a resurgence of manual transmissions in an attempt to conserve fuel and in high performance vehicles using manual transmissions, it becomes imperative that the problems of double detent, low temperature shift effort and clashing be solved. The present invention provides a solution to double detent, clashing and shift effort through the formulation of a manual transmission fluid which exhibits high dynamic friction properties as well as low static friction properties and through temperature viscosity controls.
U.S. Pat. No. 4,031,023 issued June 21, 1977 to Musser and Koch, discloses the use of viscosity improvers to impart a liquid character to a lubricating composition. Musser et al also discloses synthetic lubricating oils, extreme pressure (EP) agents and dispersants. The term dispersants as utilized by Musser et al include materials which suspend or disperse sludge and which are described as being oil-soluble, and stably dispersible in lubricating compositions.
Heilman et al in U.S. Pat. No. 3,957,664 issued May 18, 1976, discuss the use of olefin based synthetic lubricants. In particular, internal olefins or mixtures of internal olefins are combined with di-t-butyl-p-cresol to obtain a high temperature lubricant.
U.S. Pat. No. 3,929,650 to King et al issued Dec. 30, 1975 discloses borated over-based alkali metal carbonates of alkali or alkaline earth metal sulfonates. U.S. Pat. No. 3,480,548 to Hellmuth et al issued Nov. 25, 1969 discloses overbased boronated products.
Wiley et al in U.S. Pat. No. 3,944,495 issued Mar. 16, 1976, discuss various di-alkyl dithiophosphates obtained from oxylated long, straight-chain alcohols, acids or mercaptans and the use of such materials in lubricating oils. Wiley et al is concerned with automatic transmission fluids and, in particular, zinc salts which are stated to give anti-corrossion and anti-wear properties to the automatic transmission.
U.S. Pat. No. 4,119,550 issued Oct. 10, 1978 to Davis and Holden describes sulfurized olefins as lubricant additives. A further disclosure of sulfurized olefins for use in lubricants is found in U.S. Pat. No. 4,119,549 issued Oct. 10, 1978 to Davis.
Further disclosures of sulfurized olefins for lubricant formulations are found in U.S. Pat. No. 4,344,854 to Davis et al issued Aug. 17, 1982. Still further disclosures of sulfurized products useful in lubricants are found in Davis, U.S. Pat. No. 4,191,659 issued Mar. 4, 1980.
The use of calcium alkyl benzene sulfonates and polyolefins in a lubricant is found in U.S. Pat. No. 4,172,855 issued Oct. 30, 1979 to Shubkin et al. Horodysky, in U.S. Pat. No. 4,529,528 issued July 16, 1985 describes borated amine-phosphite reaction products which are useful in lubricants and fuels. Horodysky also discloses various olefin polymers which are stated to be useful in synthetic oils.
Howie et al, in U.S. Pat. No. 4,525,289 issued June 25, 1985, discloses various lubricating formulations utilizing overbased calcium sulfonate and overbased magnesium sulfonate. Trimers of alpha-decene are shown in combination with the sulfonate salts and as well with dispersants, foam inhibitors and amides in Howie et al.
The foregoing references, while generally applicable to lubricating compositions, do not specifically discuss the issue of obtaining good dynamic and static properties in a manual transmission fluid. The present invention deals with obtaining a manual transmission fluid having outstanding static and dynamic frictional properties.
Throughout the specification and claims, percentages and ratios are by weight, temperatures are in degrees Celsius, and pressures are in KPascals over ambient unless otherwise indicated. To the extent that references cited in the specification are relevant to the present invention, they are herein incorporated by reference.